1. Field of the Invention
This invention relates to telephoto zoom lenses having long focal lengths included in the zoom range thereof, and more particularly to improvements in compactness over the zoom lenses described in U.S. Pat. No. 4,094,586.
2. Description of the Prior Art
A conventional zoom lens there is composed of a 3-component front lens assembly of variable magnification power with a positive-negative-positive refractive power distribution in this order from the front, and a 2-component fixed rear assembly. The second component is axially moved to effect a change in the focal length of the entire system, while simultaneously moving the 3rd component along a path concave toward the front to effect the image shift compensation.
In general, this type of zoom lens when increased in zoom ratio and relative aperture calls for a very large increase in the physical length and the diameter of the front member thereof, thus tending to lack the compactness. In other words, the conventional zoom lenses such as those disclosed in Japanese Patent Laid-Open Publications Nos. Sho 53-131852 (German Patent Laid-Open Publication No. 2,817,633), Sho 49-899, Sho 51-37247 and Sho 51-63635 have ratios of the length from the front vertex to the focal plane to the longest focal length, or telephoto ratios, almost about unity, even at minimum, not exceeding the order of 0.97.